PMA 2010: Sigma has also taken the opportunity to reveal a bit more about its new 'FLD' glass, which is used in several of the company's lens designs simultaneously unveiled at PMA. Standing for 'F' Low Dispersion, the material is claimed to have performance equivalent to fluorite glass, but at a more affordable price. Its optical characteristics apparently allow excellent correction for residual chromatic aberration, while its lower density compared to traditional optical glass allows lighter lenses. It's used in the company's new 70-200mm, 17-50mm and 8-16mm designs.

Press Release:

New optical glass FLD (“F” Low Dispersion)

February 21, 2010: The Sigma Corporation (COO: Kazuto Yamaki, Kawasaki-Shi, Kanagawa) is pleased to announce that FLD (“F” Low Dispersion) glass, which has a performance equal to fluorite glass, has been adopted and used in our new high performance lenses.

FLD glass is the highest level low dispersion glass available with extremely high light transmission. This optical glass has a performance equal to fluorite glass which has a low refractive index and low dispersion compared to current optical glass. It also benefits from high anomalous dispersion. Using these characteristics gives excellent correction for residual chromatic aberration (secondary spectrum) which cannot be corrected by ordinary optical glass and ensures high definition and high contrast images.
FLD glass offers superior optical performance, equal to fluorite, at an affordable price.  The density of FLD glass is lower than traditional optical glass, ensuring a lighter construction of large aperture lenses.

FLD glass has been incorporated into some of our recently announced lenses; 4 elements have been included in the Sigma 8-16mm F4.5-5.6 DC HSM as well as 2 elements in both the Sigma APO 70-200mm F2.8 EX DG OS HSM and the Sigma 17-50mm F2.8 EX DC OS HSM.

Sigma, as a leading manufacturer of lenses, is continually innovative in the use of new materials and lens designs.